"The entire incident that took place on Ram Navami festival should be inquired by the NIA," Sinha told a press conference here.
Visiting the incident sites, the former External Affairs minister said he would meet Chief Minister Raghubar Das to seek a proper inquiry by the NIA.
Sinha, who visited the spots with local BJP MLA Manish Jaiswal, claimed that as per information "seventy powerful bombs and bomb-making materials were supplied to a particular group in Habibinagar colony of Khirgaon locality by a person from Kolkata who came by bus for creating disturbances in Hazaribagh".
Curfew was clamped in Hazaribagh and its surrounding areas on April 17 after two groups of people clashed, torched shops and pelted stones at policemen injuring many of them on the last day of the Ram Navami festival.
The trouble started when objectionable recorded slogans were played in a Ram Navami procession triggering clash between the two groups near Hazaribagh railway station.